The toxicity of nano-sized materials (hereinafter, nano-materials) which can be generated when the nano-materials are exposed to a human body is emerging as a new problem according to recent dramatic development of nano-technology. In consideration of the gradual increase in frequency of breath inhalation, oral inhalation and skin exposure, accurate and scientific information about nano-technology and the stability of nano-materials is urgently being requested.
The toxicity of nano-materials results from their very small size and nano-material-specific physicochemical characteristics which are largely different from a bulk-material. The toxicity such as the possibility of inducing cancer from materials having acicular structure, such as asbestos and glass fibers, has been already known for a long time. Unlike asbestos and glass fiber, the toxicity of nano-materials resulting from their very small size as well as their morphological characteristics is receiving more attention. It has been reported that high surface reactivity and cell membrane permeability allow the nano-materials to be easily introduced into a living body, enhance the possibility of inducing cellular level stress, and can further have a continuous effect by accumulating in a living body, like asbestos. It is considered that nano-materials, unlike micro-sized materials, can be deposited in the body by penetrating deeply into the body so as to cause cardiovascular diseases, and particularly, that nano-materials penetrating through a nasal nerve can move in the body by blood so as to also cause brain damage.
Most of nano-material toxicity studies conducted on living bodies are conducted by injection using syringe or cell culture, and mainly with metals, metal oxides, carbon nano-materials and the like. In general, it is known that nano-particles are introduced into a human body by the respiratory system, mouth and skin, rather than by injection.
It is time that international co-operation should be actively pushed ahead to prevent the potential harmful effects of nano-materials in advance and to make provisions for nano-materials, and an institutional strategy should be simultaneously prepared to minimize or reduce potential dangers, such as indiscriminate development and application of nano-technology, and improper disposal of nano-materials.
However, the toxicity of nano-particles and the like affecting a human body or environment may be serious, and a method to assess the actual influence of the exposure of nano-materials on the human body and environment has not been properly established yet.
Up to now, generally, the toxicity assessment method used for existing chemicals has been applied to nano-materials in many cases. However, the smaller the particle size is, the wider the surface area is so as to increase the responsiveness to living tissue and the toxicity caused thereby. Therefore, an investigation into the new physical and chemical properties of nano-materials considering the nano-sized characteristics and the toxicity caused thereby is critical.
Therefore, in order to assess the toxicity of nano-materials, there is a need to study their unique characteristics and problems, and the potential causes of their behavior, exposure and toxicity.
Recently, the direct exposure of consumers to nano-materials is dramatically increasing because many products using nano-materials are produced in various industrial fields, and many of them are consumed. Accordingly, the toxicity of nano-materials is being studied worldwide, and the importance of the development of a method for the toxicity assessment of nano-materials is also magnified. A supplemental platform for the cellular toxicity assessment of nano-materials is needed by developing a protocol, which can solve the problems arising in conventional nano-material toxicity assessments, and by developing a new instrument for nano-material toxicity assessment.
Therefore, the present inventors found that a more objective assessment of the toxicity of nano-materials is possible by analyzing characteristics of the nano-materials themselves, such as concentration (number), size, distribution and the like, using Selective Plane Illumination Microscopy (SPIM); analyzing influences (reactivity) of nano-materials on a cell using flow cytometry, image cytometry, a normal and inverted exposure apparatus and the like in sequence; and combining the results.